Automatic Rocking Chair

Designers:  Katie Myers, Anne Marie Amacher, and Meredith Cantrell
Client Coordinator:  Diane Scoggins, Hilltop Home
Supervising Professor:  Larry Bohs

INTRODUCTION
The Hilltop Home in Raleigh, NC is a residential facility for young children with profound physical and mental disabilities.  The children enjoy and medically benefit from rhythmic motion, such as rocking, but due to various disabilities, most of these children cannot rock themselves.  The Automatic Rocking Chair incorporates a glider-style rocking chair powered by an electric gear motor, and features such as a timer, child-operable switch, and speed control.

SUMMARY OF IMPACT
The Automatic Rocking Chair will medically and developmentally benefit the children at the Hilltop Home. Our supervisor, Diane Scoggins, commented, “The chair is going to be a tremendous help for staff, by freeing up caregivers who previously had to stay right beside a rocking chair to manually keep it moving…The flexibility provided by the motor’s speed control and by the positioning straps will permit us to use the chair with almost every child in our facility.  And we are so impressed with…the tray top with hand-painted designs!”

TECHNICAL DESCRIPTION
The Automatic Rocking Chair (Figure 1) design is based upon a previous NSF student project at Utah State University (Christensen and Escobar, 1995), but tailored to the needs of children at the Hilltop home.  The design translates the rotational motion of a gear motor into the translational motion of a Classic Glider Rocker by Storkcraft (model #002646350).

Components of the design are shown in Figure 2.  A fixed arm is attached to a 90V DC gearmotor (Dayton #2H577) with two setscrews to create an offset shaft.  This fixed arm is attached to a moveable arm by a bearing pin. The other end of the moveable arm attaches with a bearing onto the moveable dowel, which is made of 3/4″ aluminum rod.  When the motor is turned on, the fixed arm rotates, driving the moveable arm back and forth laterally.  This forces the moveable dowel to move laterally, thereby gliding the chair back and forth.

The motor provides 235 in-lbs of torque and operates at a maximum speed of 62 rpm. A Dart (model #5JJ58) speed control allows users to adjust the speed of the motor within a 0-30 rpm range. One rotation of the motor translates into one full swing of the chair, so the maximum rocking frequency of the chair is one swing every two seconds.  The speed control is conveniently mounted on the side of the chair and plugs into a wall outlet.

A Powerlink2 device (Ablenet, Inc.) allows children to initiate the rocking motion via a switch selected by an aide.  Because not all the children have the physical or mental ability to use this feature, the PowerLink2 also has a setting that allows the teacher to turn the device on indefinitely.

A custom adjustable-height desk provides a sturdy surface for the child-operable switch. Two wooden dowels connected to the chair slide through holes in the desk.  Two pins fit through holes in the dowels to support the desk at four different heights.

A TumbleForms child seat attaches to the chair with two Velcro straps that fit through slits on the child seat and wrap around the back of the chair. To accommodate all the children, the angle of incline of the child seat is adjustable. Finally, wheels attached to the back legs of the chair and a lifting strap attached to the front legs make the chair transportable between classrooms at the Hilltop Home. Lifting the strap upwards tilts the chair back onto the wheels so it can be rolled into an adjacent room.  Cost of parts was approximately $850.